Time Slot Management in Backscatter Systems for Large-Scale IoT Networks

Backscatter communication is considered as a key enabler of the Internet of Things (IoT). It has recently emerged as an alternative of active RF source transmission which enables devices to communicate at a very low power budget. This can be partly attributed to the information transmission configuration of the backscatter tags which makes use of ambient RF signals for reflecting the information to the receiver. Due to these characteristics, the backscatter communications have found many applications in smart homes and transportation systems. In this regard, passive and semi-passive radio frequency identification (RFID) backscatter tags are commonly available in the market. However, these backscatter systems not tags use ALOHA based anti-collision algorithms and make use of slots with a single tag response (singleton) only. The slots with multiple backscatter tag responses (collision) along with slots having no backscatter tag response (empty) are of no use and directly affect the overall throughput as well as the inventory time of the system. Though some anti-collision protocols have been proposed that try to eliminate the empty slots, such systems are still inefficient because of neglecting the transmission capability of other backscatter tags. Specifically, if multiple backscatter tag signals colliding in a single slot are decoded successfully, only the strongest of them proceed with the identification process and the rest of the recovered tag signals are discarded. The present protocol allows only single tag identification per slot. In this chapter, a novel technique is proposed to use some of the unreadable slots (i.e., empty and unsuccessful collision slots) by using the recovered RFID backscatter tags data from previous collision slots that have not proceeded with the identification process. The simulation results show improved throughput and reduced inventory time.